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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic plants other than algae

Administrative data

toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
supporting study
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies

Data source

Reference Type:
Toxicity tests of aquatic pollutants by using common duckweed
W. Wang
Bibliographic source:
Environmental Pollution B, 11, 1986, 1-14

Materials and methods

Test guideline
no guideline followed
GLP compliance:
not specified

Test material

Specific details on test material used for the study:
Test material is called Fe(III) in this article. Further details about the source of the ferric ion are not given.

Sampling and analysis

Analytical monitoring:

Test solutions

Details on test solutions:
To each jar was added a toxicant and 200 ml of plant nutrition solution (pH = 7.5). 40 fronds of duckweed were transplanted into each jar.

Test organisms

Test organisms (species):
Lemna minor
Details on test organisms:
Duckweed stock was collected from a pond located inside the Illinois State Water Survey property during the spring of 1982. The stock was maintained in the laboratory in a polypropylene tray with 20 litre capacity. To the tray was added a small amount of sediment, collected from the same pond, 10 litres of pond water and 5 litres of cold tap water. The plants were illuminated with cool-white fluorescent lights. Every 3-4 days cold tap water was added to maintain the water level. The duckweed species was identified as Lemna minor. The selected duckweed colonies were stored in deionized water and sealed from light. The purpose of the light exclusion was to prevent growth during the holding period. The colony was discarded if it grew, or if it appeared unhealthy.

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
4 d

Test conditions

not specified
Test temperature:
25 - 29 °C
Dissolved oxygen:
not specified
not specified
not specified
Nominal and measured concentrations:
6 concentration levels, not further specified
Details on test conditions:
The bioassay experiments were conducted in a series of 200 ml fruit jars. To each jar was added a toxicant and 200 ml of plant nutrient solution, the same as the algal nutrient solution suggested in Standard Methods (1980). The pH of the solution was 7.5. For each toxicant, there were six concentration levels. Unless specified, 20 colonies or 40 fronds of duckweed were transplanted into each jar. The illumination was provided by cool-white fluorescent light with an intensity of 6456 lux. Each jar was covered with a watch glass. Temperature was maintained at 27 ° +- 2 °C and the incubation time was 4 days, unless specified. Each experiment was conducted with 3-6 replicates. At the end of incubation, the number of fronds in each jar was counted with the aid of a magnifying glass. The increase of frond number was used to indicate duckweed growth and the difference between treated and control samples was used to indicate the toxic effect.
Reference substance (positive control):

Results and discussion

Effect concentrations
4 d
Dose descriptor:
Effect conc.:
3.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
Basis for effect:
frond number
Reported statistics and error estimates:
Each experiment was conducted with 3-6 replicates.

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
The EC50 (4d, Lemna minor) obtained for Iron(III) is 3.7 mg/l.
Executive summary:

In this study by Wang (published 1986) the aquatic toxicity of several toxicants to Lemna minor (Duckweed) is investigated. The plants were exposed to different toxicant levels for four days. The frond number was used as measure for duckweed growth and comparison with control samples was used to indicate toxic effects. A concentration-effect relation was used to determine EC50 values. The EC50 (4d, Lemna minor) obtained for Iron(III) is 3.7 mg/l.